1. Field of the Invention
This invention relates generally to the drilling of wells, such as for the production of petroleum products, and, more particularly, the acquisition of subsurface formation data such as formation pressure, formation permeability and the like.
2. Description of the Related Art
In oil well description services, one part of the standard formation evaluation characteristics is concerned with the reservoir pressure and the permeability of the reservoir rock. Present day operations obtain these characteristics either through wireline logging via a xe2x80x9cformation testerxe2x80x9d tool or through drill stem tests. Both types of measurements are available in xe2x80x9copen-holexe2x80x9d or xe2x80x9ccased-holexe2x80x9d applications, and require a supplemental xe2x80x9ctripxe2x80x9d. A trip typically involves removing the drill string from the well bore, running a formation tester into the well bore to acquire the formation data, and, after retrieving the formation tester, running the drill string back into the well bore for further drilling. Because xe2x80x9ctripping the wellxe2x80x9d uses significant amounts of expensive rig time, it is typically done under circumstances where the formation data is absolutely needed, during a drill bit change, or when the drill string is being removed for some other drilling related reason.
On the other hand, during well drilling activities, the availability of reservoir formation data on a xe2x80x9creal timexe2x80x9d basis is a valuable asset. Real time formation pressure obtained while drilling will allow a drilling engineer or driller to make decisions concerning changes in drilling mud weight and composition as well as penetration characteristics at a much earlier time to thus promote the selected aspects of drilling. The availability of real time reservoir formation data is also desirable to enable precision control of drill bit weight in relation to formation pressure changes and changes in permeability so that the drilling operation can be carried out with greater efficiency.
It is therefore desirable to acquire various formation data from a subsurface zone of interest while the drill string is present within the well bore. This eliminates or minimizes the need for tripping the well solely to run formation testers into the well bore to identify formation characteristics such as pressure, temperature, permeability, etc. One such technique is disclosed in U.S. Pat. No. 6,028,534, issued to Schlumberger Technology Corporation on Feb. 22, 2000, as assignee of the named inventors Ciglenec, et al. This patent is commonly assigned herewith. In this technique, a remote sensor containing sensor instrumentation and associated electronics is deployed into a formation. The remote sensor also contains an antenna and a battery to communicate with a host antenna on the drill collar while the drill string is in the well bore. Once deployed, the remote sensor measures one or more of the formation""s characteristics. After the measurement is complete, the data is stored in the remote sensor. A wireless communication channel is subsequently established between the remote sensor and the drill collar for data transfer.
The data transfer will typically occur, at least some of the time, during drilling operations. The drill string in which the drill collar is installed will both rotate and translate during drilling operations. However, the remote sensor, by virtue of its deployment into the formation, will neither translate nor rotate in any significant sense. Thus, during the data transfer, there may be rotational as well as translational movement of the collar antenna with respect to the remote antenna. Consequently, there frequently are two main aspects in regards to electromagnetic coupling between the collar antenna and the remote antennaxe2x80x94locating the remote sensor, and maintaining the communication channel for the entire data transfer once the remote sensor has been found.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.
The invention includes a method and apparatus for collecting data downhole in a well bore, even during drilling operations. The apparatus generally comprises an antenna and some associated electronic circuitry. The antenna includes a plurality of arrayed transceiver elements and the electronic circuitry steers transmission or reception through the antenna by controlling the application of power to the array elements. In operation, a transceiver unit containing such an antenna is positioned proximate a remote sensor placed into a formation. An electromagnetic signal is then steered to communicate with the remote sensor over a wireless link.